1. Field of the Invention:
This invention relates to a process for preparing stable bleomycin group antibiotics from unstable phlomycin group antibiotics susceptible to oxidation.
2. Description of the Prior Art:
Phleomycin, which is a glycopeptide antibiotic, was isolated in 1956, as disclosed in The Journal of Antibiotics, A9, 82-25 (1956); A12, 111 (1959): A12, 285-289 (1959). Isolation of phleomycin in high yield is difficult, however, because of its inherent instability under acidic conditions. Various antibiotics such as bleomycin similar to phleomycin, which are stable under acidic conditions, have been studied as disclosed in The Journal of Antibiotics, A19, 200-209 (1966). Structural elucidation studies of bleomycin group antibiotics have revealed that it possesses the following partial structure: ##SPC2##
Furthermore, structural studies of phleomycin group antibiotics have shown that it has the partial structure: ##SPC3##
These studies have also revealed that the partial structure (I) is unstable and can be readily converted to partial structure (II) to form a stable biologically active bleomycin group antibiotics.